GUDE : SPECIES OF PLECTOPYLIS. 1 3 



fig. 81;') are much thinner, and the anterior ridges of the anterior plate 

 much shorter and sligliter than i\\o?,e.o{ P. pon son by i ; they are parallel 

 instead of convergent as in P. magna. A comparison of the figures 

 will indicate differences in the palatal armature. The specmien figured 

 is in my collection and measures 19 millimetres in diameter. Figs. 

 8 a-c are natural size, while figs. 8 d-f are magnified. Fig. 8 d shows 

 the parietal and palatal armature from the posterior side; fig. 8^ a 

 part of the parietal wall with its plates ; and fig. 8/ the inside of the 

 outer wall with its folds and denticles. — (Ibid., p. 70 — 71.) 



Plectopylis leucochila, Gude. 



Shell sinistral, rather solid, discoid, deeply and perspectively 

 umbilicated, pale yellowish-corneous, finely and regularly ribbed, 

 ornamented with minute spiral sculpture. Suture almost linear, 

 spire depressed, apex scarcely raised. Whorls seven to seven and 

 a-half, a little rounded above, rather tumid below, increasing slowly 

 and regularly, the last descending abruptly and rather deeply in 

 front. Aperture roundly oval; peristome white, a little thickened 

 and strongly reflexed, the margins a little converging ; parietal 

 callus with a slightly raised flexuous ridge, separated from both 

 margins of the peristome by a little notch. Umbilicus deep, 

 widely perspective. Parietal wall with two transverse oblique plates 

 converging upwards, the posterior one rather thin, slightly sinuous, 

 and having a short ridge posteriorly at the upper and lower extremities, 

 the anterior one shorter, but much stronger and stouter, having an 

 ascending ridge posteriorly above and a short stout support posteriorly 

 below ; on the anterior side are found two strong horizontal folds, the 

 lower stout and short and becoming suddenly attenuated ; the upper 

 fold long, rather thinner, following the deflection of the last whorl and 

 terminating close to the ridge at the aperture, but not being united to 

 it ; a very thin horizontal fold rises below the transverse plates close 

 to the lower suture, runs parallel WMth it, and terminates at the ridge 

 at the aperture. Palatal folds, five : the first near tlie suture, straight 

 and nearly horizontal ; the second a little more oblique and deflected 

 posteriorly ; the third nearly horizontal, but more deflected posteriorly ; 

 all three have a slight indentation near the posterior extremity forming 

 a bead-like termination ; the fourth is vertical deflected a little ante- 

 riorly above and posteriorly below, having posteriorly a small denticle 

 near the lower extremity and another about the middle ; the fifth is 

 near the lower suture, horizontal and deflected at both extremities. — • 

 Major diameter, 15-17 millimetres; minor diameter, 1214 milli- 

 metres ; altitude, 6-7 millimetres. 



